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melki avatar image
melki asked Erick Ramirez answered

Replicas and copies of data when nodes are down

CREATE KEYSPACE machine_tools WITH REPLICATION = {
  'class': 'NetworkTopologyStrategy',
  'dc-1': 1,
  'dc-2': 3,
  'dc-3': 3
};

Let us suppose if dc-1, dc-2 and dc-3 have 5 nodes each. During write operation one node is down in each datacenter. As per the replication factor in each datacenter, is it safe to say that I will have 6 copies of a row across three datacenters.

replication
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1 Answer

Erick Ramirez avatar image
Erick Ramirez answered

Your question doesn't make sense to me. There are 7 replicas in total based on the keyspace definition you provided.

If one node is down in each DC:

During write operation one node is down in each datacenter.

then with 3 DCs you have 3 nodes down meaning that you are left with 4 live replicas. I'm not sure where you got 6 from. Cheers!

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